Clamping arrangement for blanket in printing press



Feb. 4, 1969 c, J, HERMAH ET AL 3,425,348

CLAMPING ARRANGEMENT FOR BLANKET IN PRINTING. PRESS Filed March 21, 1966Sheet of 2 INVENTQS CARL. J. HERMACH LEONARD TAFL '5 y 64", 7 ATTYS,

F6114, I HERMACH ETAL 3,425,348

CLAMPING ARRANGEMENT FOR BLANKET IN PRTNTING PRESS Filed Marat-r21, 1966I Sheet' 2 of 2 INVENTORS vCam. JPHERMACH Leo uman TAPEL I 'A-r-rvs.

United States Patent 3,425,348 CLAMPING ARRANGEMENT FOR BLANKET INPRINTING PRESS Carl J. Hermach, Westchester, and Leonard Tafel, La

Grange, Ill., assignors to Miehle-Goss-Dexter, Incorporated, Chicago,111., a corporation of Delaware Filed Mar. 21, 1966, Ser. No. 536,122U.S. Cl. 101415.1 9 Claims Int. Cl. B411 29/06 ABSTRACT OF THEDISCLOSURE A clamping arrangement for clamping a blanket in an undercutgroove in a printing press cylinder which employs longitudinallyextending springs for clamping the ends of the blanket against theundercut surfaces with a central cam shaft for selectively activatingthe springs. The springs are bowed to produce automatic takeup of ablanket as the press is run.

The present invention relates to printing presses and more particularlyto means for clamping a blanket on a cylinder in a printing press.

In letter press printing, with raised type, it is customary to cover theimpression cylinder with a layer or blanket of paper or the like,sometimes referred to as packing, for backing up the web during printingand to take the impression of the type. .In a lithographic press andother presses somewhat similar blanketing is used butfor a differentpurpose.

It is a nobject of the present invention to provide an improved clampingarrangement for gripping the ends of a blanket so that it is heldsecurely and safely on the cylinder during high speed operation. It isanother object to provide a clamping arrangement which applies agripping and tensioning force distributed uniformly from point to pointalong the edges of the blanket and which is perfectly symmetrical,establishing identical conditions at both edges, permitting use inpresses where the cylinder, depending upon web lead, may be rotated ineither direction.

It is a related object of the invention to provide a clamp for grippingthe leading and trailing edges of the blanket which has, aside from theleaf springs which it employs, only a single moving part to effectclamping and selective release at both the leading and trailing edges.Thus it is an object to provide a clamping arrangement which is easilyoperated, with release at the respective ends being obtained simply bythrowing an operating member in one direction or the other from acentral clamping position in which the operating member is locked duringnormal running of the press, with a substantial reduction in the timerequired to change a blanket.

It is a more detailed object of the present invention to provide aclamping arrangement which is of highly compact, unitary construction inwhich the parts are nested together, yet easily removable for servicingpurposes, and in which the access slot, running the lengthwise of thecylinder, and into which the ends of the blanket are tucked, may be ofminimum width.

It is a general object of the invention to provide a blanket clampingarrangement which is extremely simple and highly economical to make anduse but which is,

ICC

nevertheless, more satisfactory in function and result than the moreelaborate clamping assemblies in common use.

Other objects and advantage of the invention will become apparent uponreading the attached detailed description and upon reference to thedrawings in which:

FIGURE 1 is a typical section, partially fragmentary, and at reducedscale, of a clamping assembly constructed in accordance with the presentinvention mounted in an impression cylinder.

FIG. 2 is a side elevation, foreshortened and with a portion brokenaway, of the clamp assembly shown in FIG. 1;

FIG. 3 is a face view of the assembly, also foreshortened;

FIG. 4 is an enlarged end view corresponding to FIGS. 2 and 3 but withthe locking plate removed;

HG. 4a is an enlarged section of the cam shaft showing the relief andadjacent camming surfaces;

FIGS. 5a5c are stop motion views showing a typical clamping sequence;

FIG. 6 shows a typical tooth on one of the clamping springs;

FIG. 7 shows, at reduced scale, the profile of the locking plate;

FIG. 8 is a diagram showing the take-up which occurs during the clampingmovement;

FIG. 9 is a fragmentary section showing a modified constructionproviding constant take-up.

Turning now to the drawings, FIGURE 1 shows a clamping assembly 10recessed in a groove 11 formed in a reversible impression cylinder 12having a shaft 13. The cylinder is covered with a paper blanket 15having ends 16, 17 which are securely gripped by means to be described.The impression cylinder 12 normally cooperates with a plate cylinder(not shown) against which it bears to serve as a backup for the webbeing printed.

The clamping assembly 10 includes a block or body 20 preferably in theform of a casting having sides 21, 22 and a bottom 23 defining a centralcavity 24. Forming a continuation of the surface of the cylinder arearcuate surfaces 25, 26 separated by an access slot 27. To facilitatemanufacture and to lighten the construction, the body is formed withopenings 28, 29 which may be spaced at equal intervals along the length.For the purpose of fastening the body in place in its receiving groovein the cylinder, a series of cap screws 30 are provided. Such screws maybe inserted prior to installing the assembly in the cylinder, and thescrews may be subsequently tightened by a wrench inserted through theaccess slot, the slot having minor relief for this purpose as indicatedat 31.

In accordance with the invention the sides of the body are undercutadjacent the slot to provide a pair of longitudinally-extendingblanket-seating surfaces 35, 36 with coextensive clamping elements inthe form of springs having an adjacent cam shaft for pressing thesprings mutually outward to grip the ends of the blanket. Morespecifically in accordance with the invention a spring is used havingtwo sides, said sides being formed into U shape defining a central spacewhich is almost completely occupied by the cam shaft. Thus, referring tothe drawings, we provide a leaf spring 40 having bowed sides 41, 42 anda central base or mounting portion 43, the free ends of the springhaving blanket-gripping surfaces 45, 46

which are arranged opposite the respective blanket-seating surfaces 35,36.

The spring 40 is preferably formed of flat spring stock bent into theshape shown and with teeth in the form of a pattern of struck-outtrangular projections 47 (see FIG. 6). Such spring is hardened to thedesired degree, with the individual teeth being sharpened, following thehardening with a suitable grinding tool 48. In a practical case thespring may be formed of AISI C 1095 spring steel having a thickness ofapproximately 0.04 inch hardened to a hardness of 50-55 on the RockwellC scale with the teeth preferably having a height on the order of 0.05inch with a lateral spacing on the order of %th inch. The spring issecured to the bottom of the cavity 24 by a central row of machinescrews 52. In the normal state the spring sides 41, 42 are sprunginwardly so that each gripping surface is biased away from the seatingsurface with which it cooperates. As an approximate measure of the forceof retraction, the free ends of the spring prior to installation pressagainst one another. As is brought out in FIGS. 2 and 3, it is preferredto arrange several springs in end to end in the slot rather than in acontinuous length. The length of each spring may be on the order of fourinches to, say, ten inches, but since each spring is acted uponuniformly, as will be discussed, the average gripping force issubstantially the same at each point along the length of the cylinder.

In carrying out the invention a spring operator in the form of a camshaft extends centrally through the springs 40 over the entire length ofthe cylinder, the cam shaft being relieved along one side thereof todefine camming surfaces which press outwardly in opposite directionsagainst the spring sides when in a central, reference position to clampthe ends of the blanket under normal running conditions, with the camshaft being mounted for limited rocking movement in opposite directionsfrom the reference position for selective release of the grippingsurfaces at the ends of the blanket. Thus, referring to FIGS. 4a and 5a,a cam shaft 60 is used having camming surfaces 61, 62 which are definedby a relief 63 which extends, in the present instance, a little lessthan half way about the shaft. The shaft thus may be conveniently formedfrom a circular steel rod by machining away the material within thedot-dash outline in FIG. 4a. For the purpose of mounting the cam shaft60 for rocking movement, the ends of the shaft are received in openingsformed in end plates 71, 72 which are secured to the ends of the clampbody by machine screws 73. Interposed bushings 74, 75 may be employed toavoid wear at the engaged surfaces.

For the purpose of rocking the shaft in one direction or the other fromits reference position, and for holding it in such position, the shaftis formed with a faceted, preferably square, end 76 engageable by asuitable wrench. The locking member (see FIG. 7) is in the form of aspring plate 77 having a conforming recess 78 and secured to the body ofthe clamp by cap screws or the like 79, the plate being simply pressedclear of the end by the wrench. It is preferred to use an opening 78which is semi-square so that the locking plate engages the end of theshaft without completely surrounding it.

The sequence used by press operators in a typical installation of ablanket 15 will be apparent upon considering the views Sa-Sc. The camshaft is rocked through an angle of approximately 65 from the clampingposition so that the relieved portion of the shaft faces one side of thesprings. For example, the spring side 42 at the leading edge 16 of theblanket 15, permitting that side of the springs to withdraw from thesurfaces 36. The edge 16 of the blanket, which is pre-creased, is thentucked through the slot 27 in front of the clamping springs. Since thelatter withdraw all the way past the opposite edge of the slot, the edgeof the blanket is guided into place quickly and positively between theclamping or seating surfaces. When the blanket is bodily adjusted sothat it is straight 4 on the cylinder, the cam shaft is rotated throughan angle on the order of 130 so that it occupies the position shown inFIG. 5b in which the relief on the shaft faces the other side of thesprings, side 41, corresponding to the trailing edge 17 of the blanket.It may be noted that during the rotation of the shaft from the conditionshown in FIG. 5a to that shown in FIG. 5b clamping pressure is firstapplied, and then maintained, by the teeth of the gripping surface 46upon the leading edge 16 of the blanket. With the spring sides 41released, the trailing edge 17 of the blanket is inserted through theslot 27 as far as possible and the press may be inched forward at slowspeed to iron out any slack which may exist in the blanket so that thelatter will lie tightly on the cylinder surface.

The cam shaft 60 may then be restored, as in FIG. 50, to its centralreference position in which the cam surface 61 is rocked against thespring sides 41 causing the gripping surface 45 to be forced down intogripping engagement with the trailing edge of the blanket. Preferably,and in accordance with one of the more detailed aspects of theinvention, the spring sides are not only bowed in their original statebut the camming surfaces extend to a radial height indicated at r inFIG. 8 which is greater than that required to bring the grippingsurfaces into engagement and which is, indeed, sufiicient to increasethe curvature of the spring sides from that indicated at to thatindicated at 81. Such increase in curvature produces translationalmovement of the gripping surface in a direction to tension the blanket.The translational movement, slightly exaggerated for purposes ofillustration, is indicated at 83 in FIG. 8. Such movement isparticularly significant in the case of the last-to-be engaged end ofthe blanket since, by the time such movement occurs, the teeth 47 arefully seated in the blanket and effective, either immediately or duringthe first few revolutions of the press, to remove the last bit of slackto insure that the blanket is tight and secure.

It is found as a practical matter that impression cylinders equippedwith the present clamping assembly can be operated for long periods atthe highest printing press speeds with complete security and safety. Inthe event that any slack should develop under unusual conditions or as aresult of a particularly long run, the cam shaft may simply be cycledthrough the sequence set forth in FIGS. 5a-5c, so that the teeth acquirea new grip on the ends of the blanket, while manually urging the end ofthe blanket into the slot. Or, if desired, the modification shown inFIG. 9 may be used in which an auxiliary spring is interposed betweenthe cam and the adjacent clamping spring capable of a small amount ofcontinuous take-up. For example, a bar 90 may be used registering in agroove 91 and preferably formed in sections registering with theclamping springs, with the sections being pressed outwardly by springs92 seated in the bottom of the groove. Such springs may, for example, bein the form of a series of closely spaced coil springs or may be in theform of a single or sectional wave spring extending the length of thecam shaft. A similar set of take-up elements 90-92 are used on theopposite side of the shaft. Alternatively, the interposed springs maytake the form of an inner laminate on springs 41, 42. In any event theauxiliary springs are of such strength or stiffness as to be capable ofincrementally bowing the adjacent clamping springs. During clamp-up, theoperating sequence is substantially the same as has been previouslydiscussed in connection with FIGS. Sa-Sc, the spring 92 being partlycompressed. However, in the event that any slack develops in the blanketas the result of running, this is sensed by the take-up members by areduction in the reaction force exerted by the engaged clamping springs,so that the takeup springs 92 expand slightly thereby incrementallybowing the clamping springs and causing additional movement as, forexample, indicated at in FIG. 8.

It is one of the features of the construction that the clampingarrangement is perfectly symmetrical so that all of the forces arebalanced. Since the force vectors indicated in FIG. 5c are equal andopposite, there is no tendency for the shaft to bow or for the spring tocock bodily about its base or region of anchoring. Thus it sufiices tohave a relatively narrow base portion 43 which is held in engagementwith the bottom of the clamp body by means of a single row of light dutymachine screws, the narrow base making it possible to utilizesubstantially the entire length of each side of the spring for flexingaction.

The spring clamping sides 41, 42 being bowed in U configuration, providean elliptical inner space which is substantially filled by the camshaft, thus permitting a high degree of compactness and enabling thebody of the device to be substantially smaller in cross section than hasbeen possible in the past. Moreover, since each of the springs serves asa guide for the respective entering edges of the blanket, and because ofthe provision for wrench clearance along the edge of the slot, suchedges may be brought together much more closely than has been possiblewith prior designs so that substantially the entire cylindercircumference is blanketed. Since the springs are closely spacedend-to-end, a two dimensional pattern of gripping teeth is applied tothe blanket with complete uniformity along the entire width of thelatter insuring against any localized stress and which is to becontrasted with clamping arrangements using spaced finger elements. Eachof the springs 40 may, if desired, be of laminated construction.

While the invention has been described in connection with an impressioncylinder for a printing press, It will be understood that the inventionis not necessarily limited thereto and may be used wherever it isdesired to secure a thin sheet to the surface of a rotating cylinder.Consequently it is intended that the terms impression cylinder andblanket be interpreted in a generic sense to cover any cylinder in aprinting press having a covering sheet. It will also be understood thata plurality of clamping assemblies may be spaced about the cylinderperiphery.

We claim as our invention:

1. In an impression cylinder having a groove, a clamp ing assemblyhaving an elongated body fitted in the groove including sides defining alongitudinally extending cavity having a narrow access slot at thecenter, said sides being undercut adjacent the slot to provide a pair ofinternal longitudinally extending surfaces for seating the edges of ablanket, a pair of longitudinally extending springs secured to thebottom of the cavity having blanket engaging surfaces along the freeedges thereof arranged opposite the seating surfaces, and a controlmember in the form of a rockable cam shaft centered between the springsand relieved to define opposed camming surfaces so that when the shaftoccupies a central reference position the springs are pressed alongtheir lengths into blanket-clamping engagement with the seatingsurfaces, the springs being inwardly sprung toward the cam shaft so thatwhen the cam shaft is rocked in one direction 01: the other from itsreference position a selected one of the springs is released forinsertion of an end of the blanket.

2. The combination as claimed in claim 1 in which the springs areoutwardly bowed and in which the throw of the cam surfaces issufliciently great as to cause overtravel of the engaged portions of thesprings beyond the point of blanket-engagement accompanied by anincrease in the curvature of the springs and relative translation of theblanket-gripping surface thereon in a direction to tension the blanket.

3. The combination as claimed in claim 1 in which the springs are formedof flat spring stock arranged end to end in the groove and in which thegripping surfaces consist of an end to end pattern of closely spacedpoints struck out of the stock.

4. The combination as claimed in claim 1 in which the body has machinescrews which project through the springs in the bottom of the cavityaligned with the slot for securing the body to the cylinder and in whichthe edges of the slot are locally relieved at the screw positions foraccess of a slender turning tool.

5. In an impression cylinder having a groove, a clamping assembly havingan elongated body fitted in the groove including sides defining alongitudinally extending cavity having a narrow access slot at thecenter, the sides of the body being undercut adjacent the slot toprovide a pair of longitudinally extending surfaces for seating theedges of a blanket, a plurality of longitudinally extending U-shapedsprings secured end to end to the bottom of the cavity and havingblanket-gripping surfaces along the free edges thereof in opposedrelation to the respective seating surfaces, said springs beingoutwardly bowed to define a central space, and means including a controlmember extending longitudinally in central position in the space forbearing upon the central portion of the springs for urging them intoblanket-clamping engagement with the seating surfaces.

6. In an impression cylinder having a groove, a clamping assembly havingan elongated body fitted in the groove including sides defining alongitudinally extending cavity having a narrow access slot at thecenter, the sides of the body being undercut adjacent the slot toprovide a pair of longitudinally extending surfaces for seating theedges of a blanket, a plurality of longitudinally extending U-shapedsprings secured to the bottom of the cavity and having blanket-grippingsurfaces along the free edges thereof in opposed relation to therespective seating surfaces, and control means for spreading the sidesof the springs apart for normally urging them into blanketclampingengagement with the seating surfaces, said spring sides being inwardlysprung and said control means being selectively movable out ofobstructive position to permit each spring side to withdraw past theslot to serve as a guide for the edge of the blanket fed into the slot.

7. In an impression cylinder having a groove, a clamping assembly havingan elongated body fitted in the groove including sides defining alongitudinally extending cavity having an arrow access slot at thecenter thereof, the sides of the body being undercut adjacent the slotto provide a pair of longtudinally extending blanket-seating surfaces, aU-shaped spring secured at its center to the bottom of the body andhaving blanket-gripping surfaces at the free edges thereof opposite therespective seating surfaces, a cam shaft substantially occupying thespace within said spring and relieved along one side to define cammingsurfaces extending in opposite directions for pressing outwardly againstthe sides of the spring for urging the blanket-gripping surfaces againstthe respective seating surfaces, the sides of the spring being inwardlysprung for selective release of the gripping surfaces upon rocking ofthe camshaft through a small angle in one direction or the other.

8. The combination as claimed in claim 7 in which the central portion ofthe spring has a relatively narrow region of face-to-face contact withthe bottom of the cavity so that the sides of the spring are free toflex throughout substantially their entire length.

9. In an impression cylinder having a groove, a clamping assembly havingan elongated body fitted in the groove including sides defining alongitudinally extending cavity having a narrow access slot at thecenter, said sides being undercut adjacent the slot to provide a pair oflongitudinally extending surfaces for seating the ends of the blanket, apair of longitudinally extensive springs secured to the bottom of thecavity and having blanket-gripping surfaces along the free edges thereofopposite the respective seating surfaces, said springs being outwardlybowed to form a central space, a rockable cam shaft in said space, saidcam shaft being relieved along one side to define oppositely directedcamming surfaces so that when the cam shaft is in a central referenceposition the springs are bowed outwardly into blanket-clampingengagement with the seating surfaces and so that when the cam shaft 7 8is rocked to respective first and second positions on oppo- 2,378,478 6/1945 Harless 101415.1 XR site sides of the reference position, thesprings are selec- 3,008,410 11/1961 Bryer 101415.1 tively released fromthe seating surfaces, said shaft hav- 3,095,811 7/1963 Peabody et a1.101-415.1 ing a faceted end and means including a locking rnember3,335,663 8/1967 Harenza 101-415.1 having facet-engaging surfacesthereon for locking the 5 FOREIGN PATENTS shaft fixed against rockingmovement.

838,885 6/1960 Great Britain.

References Cited UNITED STATES PATENTS ROBERE E. PULFREY, PrimaryExaminer.

938,547 11/1909 Bevan 101 415.1 XR 10 I. REED FISHER, AssistantExaminer.

